BTR Nitrous/Propane dyno results (pic)

[MES]

Well I had my car dynoed today to test the BTR nitrous/propane system. It made 582.5 rwhp 681.9 rwtq with the nitrous and 436.2/485.2 without, giving a gain of 146.3/196.7 I used 52/28 jets. The recommended is 52/26 but I wanted to be on the safe side and put slightly bigger propane jets in. The pic below is the graph of the two pulls. The window switch was used 3,200/5,200 RPM so the torque is somewhat lower than others with the same system. It's lower because with a nitrous car the torque is very high at lower RPM's like 2,500 RPM then will taper down.

The nitrous did shift the HP curve lower. It now makes peak HP at 4,900 RPM rather than 5,200 without nitrous. I made 2 pulls with the nitrous and they were both within 2 HP of each other, so I would say its fairly accurate. In the graph below I ran both pulls up to 5,800 RPM so I could see the window switch turning on and off, and also compare it to a non nitrous pull.

I'm still somewhat concerned about the air fuel ratio. It was high, but the reading may not have been accurate. A wide band A/F gauge was used which stuck up the tail pipe. I know nothing about A/F gauges so if someone has some input jump in. It was reading high 12's-13.0 the operator stated he doesn't think it was reading correct because it had 3 settings one for gasoline, one for alcohol, and one for propane. Because the exhaust is a mixture of gas and propane there was no way to read it properly. I think someone stated before the best way to check the A/F was to use the one that tapped into the o2 sensors?? not sure. Anyway with the nitrous off the A/F was between 12.0-12.5 which seems about normal. Using Roe's A/F gauge the last or the 2nd to last light normally is on at WOT with the nitrous off. With the nitrous engaged the last light stays on. According to Roe the last light is 12.5 or richer, how accurate it is I don't know.

I adjusted the WOT switch to trigger when the accelerator is about 1/2 to 1/4 of an inch from the floor. (Thanks Tom for the adjusting tip) I have minimal wheel spin when the nitrous engages, if I'm at WOT before the window switch kicks in. When I was trying the system without the window switch I would get a lot of wheel spin, especially from a roll. Mostly because the weight could not get transferred to be rear wheels before the nitrous engaged.

I will be trying it at the track soon and will post the results.

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[treynor]

Excellent stuff. Your dyno graph looks very familiar. Chalk up another one for Tom's NOS kit!

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[Anthony - 98 GTS]

Congratulations on the great numbers!! Very impressive.

 

[Tom Welch]

Mike,

Nice numbers! Here are a few things to try;

Set the low rpm to 2500 and your torque will increase to over 700 ft/lbs. Try a larger propane jet for even more torque but no loss in power.

Your a/f is not lean. A larger propane jet will help richen your mix.

Remember that with these dyno pulls the initial spike of a/f is equal to what you might see from the initial burst of power.....as if you were leaving the starting line. I know that dyno pulls are done in 4th gear, but it is a function of elaspsed time for the computer to compensate for mixture. If you made a dyno pull shifting through the gears you would find that the car would continue to richen until max injector cycle was realized. We have tried it. Shifting through the gears with over 700 ft/lbs of torque is ******* the dyno drum, so most shops don't allow it.

Again, beautiful numbers. Get that beast to the track!

HI BEN, I've missed seeing your posts!

Happy Holidays,

Tom
Http://btrviper.com

 

[MES]

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Again, beautiful numbers. Get that beast to the track!
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I will try it tonight if all goes well.


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
window switch to shut down the NOS at 5200 rather then, lets say 6000rpms
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I have a set of switch plugs, in 200 RPM increments from 3,000 - 3,800 and 5,000 to 5,800 which I can use to play with. I put in 3,200 and 5,200 for the dyno pull so I can see it turn on and off. I have 3,000 and 5,400 in it normally to prevent accidental activation too high or low.


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What is the cause of that dip in HP and Torque at about 3800?? It like a a little hickup.
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I think its the nitrous going from a gas state to a liquid state at the fogger nozzle. This was the first nitrous pull after 2 N/A pulls so under the hood it was quite hot. I believe at a temperature of 98 deg (under pressure) the nitrous changes from a liquid to a gas. So that means the nitrous fogger, lines & solenoid must be below 98 deg otherwise it will just spray gas rather than liquid nitrous. If you look at 3,600 RPM the HP gain was about 100 then look at 4,400 the gain was 150 HP this would indicate the change from gas to liquid. I did a 2nd pull with nitrous 2 minutes after the first and the graph was smoother than the first, probably because it was already cooled down. I could have purged the system first and would have gotten a better low RPM numbers but since this was the very first pull with nitrous I wanted to be conservative.

Once the nitrous changes to a liquid it will continue to flow liquid through all the gears. Nitrous lines will get very cold when flowing. I think the nitrous comes out at -120 deg into the engine, so it cools everything down fast.

Also as a side note, the VEC1 did NOT effect the A/F ratio. I tried one more nitrous pull and set the high side to +8 (richer) and it had no effect on the A/F and also had no effect on the HP.

 

[Tom Welch]

Dan,

The nitrous brings down both the peak power and torque rpms considerably. To shift out of the power band is wasting both nitrous and time. To shift much above peak torque is actually wasting time as well......considering the weight and gearing of a Dodge Viper.

Tom
Http://btrviper.com